The topic of the Catholic Church occurs many times throughout Boccaccio's medieval collection of stories, the Decameron, often depicting it as corrupt and disorganized due to its unchallenged dominion throughout medieval Italy.
The first story of the first day is about Ser Cepparello or Ciapelletto who was a wicked man, but falls mortally ill and lies to his confessor about the purity of his life while lamenting over insignificant sins. When Ciapelletto dies, his confessor lectures about the goodness of Ciapelletto's life, causing the parishioners to revere his life, and later this evil man is made a saint. The character of Ciapelleto reveals how the Church creates saints out of sinners.
The fourth tale of the first day discusses a monk and an abbott who engage in sexual intimacy with a woman, and using their knowledge about the other to prevent individual prosecution. These two characters show that men who have taken orders of chastity have not been true to their word or the faith.
The first tale of the third day is about Masetto da Lamporecchio who pretends to be mute to get work at a convent. All of the nuns receive sexual satisfaction from him in turn. These characters show how women who have taken orders of chastity are also not chaste.
In probably the most risqué tale, the last of the third day, the naive young woman Alibech goes into the forest trying to be closer to God. Finding the monk Rustico, she is deflowered, being told this will "put the Devil back into Hell," and that by doing this she will better please God. In the figure of Rustico we see not only an unchaste monk, but also a rapist.
The second tale of the ninth day treats an abbess who attempts to condemn a nun in bed with her lover. In so doing, she puts on the pants of the priest she was in bed with, instead of her veil, and is seen for the hypocrite she is.
As revealed in these tales, people treated religious figures with contempt, jocularity, and sometimes (though seemingly rarely in the Decameron) with respect. For example, though Boccaccio is revealing the disorganized nature of the Church in his figure of Ciapelletto, we also see how parishioners can highly respect a man who is supposedly virtuous.